Such a traffic generator is an essential test tool for devices which are to be used in Asynchronous Transfer Mode or ATM networks and thus plays an important role in the emergence of such networks. To realize this goal, the packet information stream generated needs to have predetermined characteristics based on individual characteristics of the traffic sources, such as their mean and peak bit rates.
This necessitates the calculation of the actual characteristics of the traffic sources, i.e. their actual bit rates, from their mentioned individual characteristics as well as the selection of the source for which a packet has actually to be generated. This computation is slow compared to the transmission rates in ATM networks, even if state of the art technology is used, and has therefore to be done off-line.
In a possible traffic generator each individual source related data relates either to exactly one source or to none of the sources, and the mentioned generation means generates, upon reading the latter data, a packet for this source or an idle packet respectively. This memory is initialized beforehand according to the individual characteristics of the traffic sources.
In order to realize a long non-repetitive information stream without having to provide an unfeasibly large amount of memory, modifying means have to be provided for performing a periodic off-line computation to update the actual bit rates of the traffic sources according to their characteristics and to modify the individual source related data accordingly.
A drawback of the above described traffic generator is that the latter off-line computation has to take all new actual bit rates into account simultaneously so as to define a new series of individual source related data. Indeed, any update of the generation memory for one source requires that some individual source related data need to be reallocated, so inevitably affecting sources to which these individual data were previously allocated.
Such a computation is complicated and therefore also time-consuming, especially when the traffic generator needs to generate information packets for a large number of traffic sources. This results in relatively long delays in updating the generation memory and hence in a relatively long repetition, for a given storage capability of the generation memory, of the sub-optimal solution arrived at by the above computation. This generator therefore is both complicated and restricted in accuracy.